Middle-Term Surgical Outcomes of Microscopic Posterior Decompression for Far-Out Syndrome

Abstract

Far-out syndrome (FOS) is a rare incident caused by L5 nerve root entrapment in the far-out area, the L5-S1 extraforaminal area between the transverse process and the sacral ala. The purpose of this study is to disclose the middle-term surgical outcomes of microscopic posterior decompression in the far-out area (MPDFA). From June 2008 to November 2010, eight patients with FOS (six men and two women, mean age 65.4 years) were treated with MPDFA. Their chief complaint was leg pain in the L5 nerve root distribution area. Nerve root impingements in the far-out area were confirmed by magnetic resonance imaging, computed tomography and selective radiculography. Indications for MPDFA were given when pain was uncontrollable with conservative treatments for more than 1 month. MPDFA was performed according to the following procedure: a 4-to-5-cm skin incision was made just above the far-out area. The far-out area was exposed using Wiltse's intermuscular approach. The nerve root was decompressed with partial resection of the transverse process and the sacral ala, and removal of the iliolumbar ligament. Surgical outcomes were evaluated at periodical examinations with the Japanese Orthopedic Score (JOA) and a Visual Analogue Scale (VAS) of the leg pain. The mean follow-up period was 24.3 months (ranging from 12 to 40 months). All patients had reduced radicular leg pain after their operations. The mean postoperative hospital stay was 11.4 days, and the patients returned to their normal activities of daily living immediately after discharge. Both JOA and the VAS scores improved after surgery. The scores temporarily worsened in two patients with degenerative scoliosis; the worsening was attributed not to recurrence of the radiculopathy but to pain arising from knee arthropathy. The scores were maintained in the other patients at least until the final examinations during the follow-up. MPDFA is a less-invasive surgery for treating FOS and can provide a good middle-term surgical outcome.